1. Field of the Invention
This invention relates to bicycle chain shifting apparatus in which derailleur chain guides are positioned by cable movement. The invention moves derailleur cables to comply with rider-selected pedal pressure and pedal-cadence rate.
2. Description of Related Art
Automatic shifting a derailleur-equipped bicycle involves these problems:
1. Manually shifting a derailleur system demands a greater level of expertise and technique than many riders are willing to develop. However, completely automatic chain shifters also limit the utility of bicycles so equipped. PA1 2. Imperfect timing of a chain shifting event may occur while the chain is at high stress, causing unnecessary mechanical wear to the chain and sprockets, and inducing an unnecessary loss-of-balance risk for a rider. PA1 3. Transferring optimum power from a rider to the bicycle pedal system requires multiple attention of the rider to pedal force and pedal-rate cadence while steering and balancing the vehicle. PA1 1. A rider may let the automatic shifting feature operate or may use manual shifting capability. PA1 2. Timing of a high-tension chain shift is automatically coordinated with the minimum chain force of a rider's pedal-stroke. Equipment wear and rider risk are reduced. PA1 3. Rider attention need not be distracted by needs to manually direct derailleur to shift chain among sprocket options.
An automatic bicycle transmission (U.S. Pat. No. 4,598,920) sensed the angular velocity of a rear bicycle wheel and guided a pedalled chain onto a smaller driven sprocket as angular velocity increased, or larger driven sprocket as angular velocity decreased.
A "Chain Shifter" (U.S. Pat. No. 5,407,396), cited as a reference, automatically adjusts cable movement in response to pedal pressure peaks and low force patterns.
A "Derailleur Cable Collet" of Docket R395 automatically adjusts cable movement in response to pedal pressure and pedal velocity whose threshold presets may be electrically overridden by transducer inputs through other decision logic apparatus.